5.  The applicant was born in 1939 and currently lives in Pirot.
6.  The facts of the case, as submitted by the parties, may be summarised as follows.
7.  On 14 September 1990 the applicant was granted an old-age pension as from 1 September 1990 by the Pirot branch (Filijala Pirot) of the Serbian Pensions and Disability Insurance Fund (Republički fond za penzijsko i invalidsko osiguranje zaposlenih – hereinafter “the Fund”).
8.  Following a successful claim for unpaid wages against his former employer, on 8 December 1993 the applicant asked the Fund to amend its decision of 14 September 1990. In particular, he asked the Fund to apply a more favourable period for the calculation of his base pension and to increase his pension on account of the additional income that he had earned in the period before retirement (during 1989-90) which had not initially been taken into account (da se utvrdi nov penzioni osnov i izvrši obračun razlike u plaćanju).
9.  Following a remittal, on 16 May 1994 the Fund issued an amended decision (hereinafter “the 1994 decision”): (i) establishing a new increased pension (14,015.66 old dinars (YUD)); (ii) establishing an increased "base pension" (penzijski osnov) to be applied from 1 September 1990, applying an adjustment rate of 45.30% as from 1 January 1991 and another adjustment of 28.13% as from 1 April 1994; (iii) determining that a supplementary pension should be paid on the basis of the difference between the pension received for the prior period starting on 1 September 1990 and the new pension granted retroactively by this decision; and (iv)  noting that the calculations for the pension were attached to the decision and formed an integral part of it. In addition, the reasoning in the 1994 decision contained an exact figure to be used as the base pension and determined that the applicant’s pension should be 85% of that amount.
10.  The decision of 16 May 1994 became final on 22 July 1994.
11.  On 31 December 2003 the applicant lodged a motion with the Pirot Municipal Court (“the Municipal Court”) for the enforcement of the part of the 1994 decision concerning the outstanding supplementary pension, and also sought payment of statutory interest from 25 January 1994 on the amounts due. The applicant supplied, together with his request for enforcement, an expert’s calculation determining the exact amount due.
12.  On 20 January 2005 the Municipal Court issued the enforcement order as requested.
13.  On 3 February 2006 the Municipal Court quashed that enforcement order following the Fund’s objection (prigovor) that there was no proof that the 1994 decision was enforceable.
14.  On 16 February 2006 the Municipal Court requested that the Fund provide it with a reissued copy of the 1994 decision containing an enforceability clause (klauzula izvršnosti) within three days. On 22 February 2006 both the Fund and the applicant supplied the court with reissued copies of the 1994 decision containing an enforceability clause.
15.  On 15 March 2006 the Municipal Court rejected the applicant’s fresh enforcement request. The Municipal Court firstly noted that the 1994 decision had established the applicant’s entitlement to a pension, his base pension and the date on which the applicant had acquired his right to a pension. The court found, however, that the decision in question was not “liable to enforcement” as it had not set the exact, total amount to be paid, which rather had been subject to recalculations depending on statistical data. It concluded that the outstanding debt should be therefore established only in special administrative proceedings conducted by the Fund’s accounting department - apparently the so-called “likvidatura”.
16.  On 23 March 2006 the applicant lodged an objection against the decision of 15 March 2006, claiming that the enforcement request had contained all the figures and information necessary to calculate the amount due, also supplying an expert opinion to that effect.
17.  On 26 June 2006 the Municipal Court upheld the decision of 15 March 2006. The competent panel, in particular, (i) noted, without making reference to the applicable domestic law, that the applicant should have asked for the mandatory enforcement of the 1994 decision in the administrative proceedings (prinudno izvršenje u administrativno-upravnom postupku (sic.)); and (ii) summarised the Supreme Court’s reasoning in the preceding civil proceedings concerning the application of the principle of monetary nominalism and revaluation of the claim (see paragraph 24 below).
18.  In the meantime, as the Fund had failed to pay the supplementary pension to the applicant, on 25 January 1996 he filed a civil claim with the Municipal Court for the determination and payment of the outstanding supplementary pension as from 1 September 1990, and also sought statutory default interest and damages to compensate him for the effects of inflation (naknada inflatorne štete) and maladministration on the part of the Fund.
19.  During the proceedings, on 26 May 1997, a court-appointed financial expert determined the nominal amount of the supplementary pension for the period between 1 September 1990 and 24 January 1994. The expert utilised a method of revalorisation of the pecuniary claims (metod valorizacije novčanih potraživanja).
20.  On 8 April 2001 the court obtained an additional expert report on the statutory default interest accrued as from 17 May 1994 to that date.
21.  Following two remittals, on 12 June 2001 the Municipal Court, noting the pension payment slips issued between 1990 and 1994, as well as the exact amounts of the new pension and the base pension as determined by the 1994 decision, awarded the applicant the outstanding difference in the pension actually paid and the applicant’s pension entitlement, plus statutory interest accrued, as well as costs.
22.   On 4 December 2002 the Pirot District Court upheld the judgment of 12 June 2001. It clarified, as regards the Fund’s appeal, that the impugned dispute could not be the subject of administrative proceedings, as the applicant had not challenged the lawfulness of the 1994 decision, but rather had sought the payment of the pension debt and damages.
23.  Following a remittal in the enforcement proceedings, on 6 March 2003 the Municipal Court ordered the enforcement of the judgment of 12 June 2001. On 24 July 2003 the awarded amount, including the accrued statutory interest, was transferred from the debtor’s account to that of the applicant.
24.  Acting upon the Fund’s subsequent appeal on points of law, on 19 June 2003 the Supreme Court overturned the lower courts’ judgments. It stated that (i) in accordance with the law of obligations (the principle of monetary nominalism), the applicant was not entitled to damages to compensate him for the effects of inflation or any damages whatsoever in disputes of a public-law nature (such as the one in question); (ii) pension rights could only be established or enforced through administrative proceedings (“administrativno-upravni postupak”); (iii) even assuming that the Fund’s debt was to be considered as a statutory obligation, the applicant could not be awarded statutory interest in the civil proceedings (being a condition for a revaluation of the nominal claim), as the administrative enforcement of the 1994 decision had not been sought; (iv) the applicant could arguably seek such an award in enforcement proceedings; and (v) each party should cover its own costs and expenses. Lastly, the Supreme Court appears not to have addressed the nominal debt in its judgment.
25.  On 7 August 2003 the Fund filed a motion for recovery of the entire sum paid to the applicant on 24 July 2003 (see paragraph 23 above) in view of the decision of the Supreme Court of 19 June 2003.
26.  On 19 September 2003 the Municipal Court issued an enforcement order whereby half of the applicant’s pension was to be transferred to the Fund’s account each month until the sum had been repaid in full. It would appear that for the purpose of securing the debt the Municipal Court blocked the applicant’s access to his entire pension for a certain period of time.
27.  By 30 August 2010 the applicant had repaid the total amount that he was required to pay in accordance with the above order.
28.  The Pirot Branch of the Fund informed the Government that it was undisputed that it had failed to pay the difference between its past payment and the applicant’s pension entitlement for the period between 1 September 1990 and 31 December 1993. In that regard, the Fund explained that it had been unable to calculate and pay its debts that arose during the period of high inflation in Serbia to all beneficiaries of the pension insurance system, including the applicant, due to limitations in its computer software (iz tehničkih i programskih razloga).
29.  The pension system in Serbia is a “pay as you go” system. The Fund is a State administrative body which is tasked with awarding and administering pensions and disability insurance payments. It is a legal entity authorised to levy compulsory social insurance contributions, in accordance with the rights and obligations determined by applicable law and its internal regulations. All pension and disability insurance contributions are transferred to the Fund’s accounts, together with the funds paid by the central government of the respondent State. The State guarantees the Fund’s obligations.
30.  In the period between 1984 and 1994, the domestic currency heavily depreciated on several occasions, resulting in its redenomination on a number of occasions. In 1993 the annual inflation rate was calculated at more than 1.5 billion per cent, while the average daily rate of inflation was nearly 100 per cent. In October 1993 the Government created a new currency unit. One new dinar was worth one million of the "old" dinars. On 24 January 1994 the government introduced the "super" dinar, equal to 10 million new dinars.